Five things we learned in Arsenal's 2-1 defeat away to Villareal in the first leg of the Europa League semi-final.

1. When the tie was seemingly over, Arsenal found a way to stay in it. Two goals in the opening half an hour from Manu Trigueros and Raul Albiol cued a considerable degree of alarm in the Arsenal camp yet Nicolas Pepe’s second half penalty dragged the visitors back into a contest they looked to be out of at half time. Whilst the Gunners were below par in the early stages, they dug deep, showing a great deal of resilience and fortitude to grab what could turn out to be a priceless away goal.

2. Dani Ceballos is a very lucky man. Sent off for leaving a boot on Daniel Parejo, Ceballos could have cost his team dearly, as his recklessness forced Arsenal to play the majority of the second half with ten men. Heavily inconsistent in a second successive spell on loan in north London, the Spaniard’s actions against Villarreal on Thursday night could be the final nail in the coffin when it comes to his future at Arsenal.

3. Taking a gamble with his starting line-up didn’t pay off for Arteta. With Alexandre Lacazette and Pierre-Emerick Aubameyang both working their way back to full fitness, the Arsenal manager deployed Pepe, a winger by trade, as a false nine. Although the Ivorian scored from the spot, he was part of an attacking unit that managed just one shot on target from open play, a statistic which will need to be much higher if Arsenal are to progress to the Europa League final.

4. After a mistake in Arsenal’s last game against Everton, Bernd Leno redeemed himself. Producing two solid saves following the dismissal of Ceballos, the German goalkeeper seemed more like his solid, reliable self. Despite some fans baying for his blood with former colleague Emiliano Martinez impressing at Aston Villa, Leno bounced back impressively against Villarreal, proving himself worthy of a place between the sticks.

5. The tie is on a knife-edge, perfectly set up for a nail-biting second leg. Unai Emery will rue the fact that his current side did not put his former to the sword and, as such, Arteta is still in with a chance of guiding the Gunners past their previous manager. Manchester United look all but assured of a place in the Europa League final after thrashing Roma 6-2, but the fate of their Premier League rivals looking uncertain by contrast. Next week, Arsenal must advance past Villarreal at all costs, but the events of the first leg demonstrated that achieving such a task will be far from straightforward.